Member
I purchased a 99 miata with a "seized" engine for $700 recently. Ends up the engine turns just fine, but the exhaust cam tried to take a vacation. In its escape attempt, it over extended a valve on the #1 cylinder causing the damage in the pic. I'm pretty sure what I'm going to hear is "Any damage to a piston is too much damage", but I wanted a sanity check before I pull the engine and replace all the pistons.
Veteran Member
Hard to see any obvious damage...clean it and repost? Have the head checked for straightness...cant imagine a cam creating this problem. Overheat and or overreved create havoc. If the valve is still seated this could be old...or was the valve broken and bent? If so something failed in the assembly...lifter, spring, spring keeper. valve. Though I dont think the piston is a problem, something absorbed the shock in those items connected together...piston, rod, bearings, crank. In the end...what you do to fix is dependent on what the engine is rebuilt for!
Ron
RAmotorsports
Member
This will be for Spec Miata, so I ended up ponying up for a full new engine when I thought of all the other things that could have been wrong with that engine. The cause of failure on the one in the car looks like it was the head gasket installed backwards. They also had a heater core bypass line made of garden hose that was crimped. Definitely time for a new engine 
Colin
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